(a) Field of the Invention
The present invention relates to a styrenic thermoplastic resin composition, particularly to a styrenic thermoplastic resin composition comprising a non-halogen flame retardant having superior flame-retarding properties and impact strength.
(b) Description of the Related Art
Rubber-modified styrene resin has superior processability and physical properties. In addition, it has superior appearance and impact strength and thus it is largely used for electric and electronic appliances and office appliances. When used for electric and electronic appliances and office appliances, a great deal of heat is produced and there is a danger of fire, and thus the resin used should have flame-retarding properties. Therefore, many studies for imparting flame-retarding properties to rubber-modified styrenic resin having flammable properties have been conducted.
As a result of many studies over a long period of time, it is known that the use of halogen compounds as flame retardants is the most effective method to make rubber-modified styrenic resin flame retardant. Also, it is known that tetrabromobisphenol A and brominated epoxy, etc. are the most commonly used halogen containing flame-retardants, and that antimony compounds have synergistic effects for flame-retarding properties.
However, halogen compounds are known to produce gases corroding metallic parts during processing, and to decompose during firing to discharge toxic gases that are noxious to the human body. Particularly, brominated compounds are criticized and restricted around Europe because they may produce environmental hormones that are noxious to the human body, such as dioxins or furans when combustion. Antimony compounds are also classified as toxic material.
Accordingly, studies of flame retardant resin compositions that do not use halogen compounds and antimony have attracted a great deal of attention. Because it is difficult for rubber-modified styrenic resin to have superior flame-retarding properties if using a non-halogen flame retardant, the development of methods for blending polycarbonate and rubber-modified styrenic resins have been attempted many times. However, a blend of polycarbonate/rubber-modified styrenic resin can achieve the desired flame retardant properties only if 70 wt % or more of polycarbonate is used. Also, if polycarbonate is used such a high level, advantages of rubber-modified styrenic resin cannot be utilized and it becomes unfavorable in terms of processability and economy.
In addition, red phosphorus or expandable graphite can be used in the resin composition in order to make rubber-modified styrenic resin flame retardant without using a polycarbonate. But, in this case, physical properties are inferior and only a dark colored product can be prepared.